The present invention relates to a method of cultivating cells of animal and human tissues and to an arrangement for performing the method.
Methods of and arrangements for cultivating cells of animal and human tissues have been already proposed in the art. When the cells are to be grown they are introduced into a nutrient solution and maintained in the latter in a suspended state. At the same time, required conditions for growth of the cells are established, such as a predetermined temperature, concentration of oxygen and the like.
If the liquid nutrient solution containing the cells is enclosed in a container and stands immovably therein, the cells have a tendency to settle on bottom and walls of the container inasmuch as their specific weight is greater than that of the nutrient solution. In this case the cells form substantially compact deposits which hinder the diffusion required for supplying the cells with oxygen. Cells which are not sufficiently supplied with oxygen will, of course, perish as is well known.
The above problem has been recognized in the art and methods of cultivating the cells have been proposed, including forcedly moving a suspension of the cells in the the nutrient solution. In such a method the nutrient solution is brought into movement by a mechanical stirrer, magnetic stirrer, vibration mixer or the like. At the same time, oxygen is admitted into the container which encloses the nutrient solution containing the cells. The above method has been proved to be satisfactory when the cultivation of the cells is performed in a substantially small container and with a substantially small quantity of nutrient solution. However, when cultivation of the cells is performed in larger containers and with a greater quantity of the nutrient solution, some difficulties develop.
First of all, working elements of the above stirrers and mixers, such as stirring blades, produce a relatively great shearing force which essentially mechanically damages the cells and thereby impedes the growth of the cells. Further, the large arrangements needed require substantial apparatus expenditures for moving the stirring or mixing working elements. In addition, when a mechanical stirrer is used, a shaft of the stirrer extends through an opening in a wall of the container and lubricating of the shaft, which is necessary for operation, results in difficulties in maintaining the sterility of the contents of the container. Finally, in the case when a great quantity of the nutrient solution is enclosed in a large container, oxygen which is supplied in an oxygen-containing gas produces, in the presence of the moving stirring or mixing elements, an undesirable foam.